Medical Microbiology - PowerPoint Presentation

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Medical Microbiology Dr. Oruba lec.3

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Microbial Metabolism

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It’s the growth, nutrition, Andmetabolism OF BACTERIAWhat does physiology means ?

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MetabolismMetabolism: Is the sum of all chemical reactions in the body. metabolism is divided into two types of classes: catabolism and anabolism.

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-Catabolic reactions supply both energy and the basic structural elements for the synthesis of specific bacterial molecules. -In the anabolic reactions , the energy requirement is consumed in form of light or chemical energy—by photosynthetic or chemosynthetic bacteria, respectively.

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6Metabolism; It includes all the chemical reactions that occur in the cell, which include two processes;1- Anabolism; all the chemical reactions that building up of cell structures and constituents where these reactions require energy.

2- Catabolism; all the chemical reactions that lead to the breaking down of macromolecules in to small and simpler ones where it leads to production of energy.Oxidation of carbohydrates to form carbon and energy source…………………..Hexoses

and

pentoses

are the major

monosaccharides

sources………

Funneling into the major pathways……..

Degradation of bigger molecules into smaller ones………..

Formation of end products……

 

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Dr SalehMicrobiology7

Assimulation (anabolism): energy-requiring

Dissimulation

(catabolism): energy-acquiring

Focal metabolites:

metabolic intermediates that link anabolic and catabolic pathways.

Glycolysis

Pentose phosphate pathway

TCA cycle

Respiration (aerobic and anaerobic)

Fermentation

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CarbonStructural organic molecules, energy sourceChemoheterotrophs use organic carbon sourcesAutotrophs use CO2The Requirements for Growth: Chemical Requirements

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11 *According to the source of energy, organisms are divided into two groups;Phototrophs; convert radiant energy from sunlight into chemical energy…..Chemotrophs; transfer energy from organic or inorganic molecules into specific energy molecules………

*According to the source of carbon, organisms are divided into two groups;Heterotrophs; use organic or inorganic chemicals( other than CO2) as a source of carbon…Lithotrophs

(

autotrophs

); their source of carbon is by fixation of CO

2

from the atmosphere….

 

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Therefore, organisms in general, are divided into four groups; 

Nutritional group

Carbon source

Energy source

Examples

1-

2-

3-

4-

Chemolithotrophs

Chemoheterotrophs

Photolithotrophs

photoheterotrophs

CO

2

Org.comp

.

CO

2

Org. comp.

Chemicals

Chemicals

Light

Light

Sulfur bact., iron bact.,….

Higher animals including human, most eukaryotic organisms,….

Green plants, most algae…..

Some

cyanobact

., some algae.

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13On the basis of the kind of electron acceptor, energy, in the form of ATP, in microorganisms is produced by 3 ways;Fermentation; it is an oxidation-reduction process for the production of energy, where the electron donors and electron acceptors both are organic compounds….and the amount of energy produced is only 2 ATP.Aerobic respiration; it is an oxidation-reduction process for production of energy where the electron donors are either organic or inorganic compounds, and the final electron acceptor is oxygen….and the amount of energy produce is 36 ATP.Anaerobic respiration

; it is an oxidation-reduction process, where the electron donors are either organic or inorganic compounds, and the electron acceptor is inorganic molecules, such as; NO-3, NO-2, SO4

- -

, CO

2

, H

2

S, …….etc. The amount of energy produced is only

1 or 2 ATP.

 

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14*Mechanism of electron transport and oxidative phosphorylation is basically the same in aerobic and anaerobic respiration, but differs in the followings:Type of the electron acceptor..Amount of the energy producedThe terminal enzyme component in electron transport system in

anaerobes is not cytochrome oxidase but other enzymes such as reductases…

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NitrogenIn amino acids, proteinsMost bacteria decompose proteinsSome bacteria use NH4+ or NO3A few bacteria use N2 in nitrogen fixation

SulfurIn amino acids, thiamine, biotinMost bacteria decompose proteinsSome bacteria use SO42



or H

2

S

Phosphorus

In DNA, RNA, ATP, and membranes

PO

4

3



is a source of phosphorus

The Requirements for Growth: Chemical Requirements

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Trace ElementsInorganic elements required in small amountsUsually as enzyme cofactorsThe Requirements for Growth: Chemical Requirements

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Organic Growth FactorsOrganic compounds obtained from the environmentVitamins, amino acids, purines, pyrimidinesThe Requirements for Growth: Chemical Requirements

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Complex polysaccharide Used as solidifying agent for culture media in Petri plates, slants, and deepsGenerally not metabolized by microbesLiquefies at 100°CSolidifies ~40°CAgar

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Culture Medium: Nutrients prepared for microbial growthSterile: No living microbesInoculum: Introducing of microbes into mediumCulture: Microbes growing in/on culture mediumCulture Media

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Sterile Mannitol Salt Agar

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Streak Plate

Figure 6.10a, b

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Nasal swab sample on Mannitol Salt Agar (MSA). Non-mannitol fermenter on left. Mannitol fermenter on right, viewed from bottom

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References: 1- Jawetz, Melnick, & Adelberg’s.( 2013). Medical Microbiology (Twenty-Sixth Edition).2- Kenneth Todar. (2008).Todar’s Online Textbook of Bacteriology ,University of Wisconsin. 23

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Thank you